What I read was $30 + a voice plan, so it's $30 + a voice plan starting at $30 = at least $60, not the original $60 plus another $30 = $90. I don't know why they didn't just call it "unlimited"; probably out of fear that people would rake them over the coals for another "unlimited data" thing like the current "unlimited" data plan. However, AT&T's "unlimited" plan in the US is capped at 5 GB, which, last I checked, is less than 6 GB.
I think 6 GB is plenty for most users; it'll certainly be fine for me, especially considering the possibility of using an open wireless network in the city (what are you planning to download that you'll use significantly over 6 GB of 3G data a month on an iPhone that only has 8-16 GB of space to begin with? Do you really watch that many YouTube videos? Are you planning on streaming video 24/7?) My concern is still around a) total cost once you have a half-decent voice plan, voicemail, etc. and b) the limited-time nature of this offer. I'd like to see Rogers stop screwing around and offer a permanent "unlimited"/high-download-cap data plan, and better rates on necessities like voicemail.